example of f2py using openmp (hello world)

README.md

This works (build with this command: f2py -c -m omp_hello omp_hello.f90 --f90flags="-fopenmp" -lgomp):

program hello

  call hellofunc

end

subroutine HELLOfunc

  INTEGER :: NTHREADS, TID, OMP_GET_NUM_THREADS, OMP_GET_THREAD_NUM

  ! Fork a team of threads giving them their own copies of variables
  !$OMP PARALLEL PRIVATE(NTHREADS, TID)

  ! Obtain thread number
  TID = OMP_GET_THREAD_NUM()
  write(*,*) 'Hello World from thread = ', TID

  ! Only master thread does this
  IF (TID .EQ. 0) THEN
    NTHREADS = OMP_GET_NUM_THREADS()
    write(*,*) 'Number of threads = ', NTHREADS
  END IF

  ! All threads join master thread and disband
  !$OMP END PARALLEL
end 

Use like follows:

┌─[pwolfram][shapiro][~/Downloads/f2yp_openmp][17:07]
└─▪ ipython 
import Python 2.7.13 | packaged by conda-forge | (default, Mar 20 2017, 14:26:36) 
Type "copyright", "credits" or "license" for more information.

IPython 5.4.1 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.

In [1]: import omp_hello

In [2]: omp_hello.hellofunc()
 Hello World from thread =            1
 Hello World from thread =            5
 Hello World from thread =            3
 Hello World from thread =            2
 Hello World from thread =            0
 Hello World from thread =            6
 Hello World from thread =            7
 Hello World from thread =            4
 Number of threads =            8

or build in pure fortran:

┌─[pwolfram][shapiro][~/Downloads/f2yp_openmp][17:09]
└─▪ gfortran omp_hello.f90 -fopenmp -lgomp
┌─[pwolfram][shapiro][~/Downloads/f2yp_openmp][17:09]
└─▪ ./a.out 
 Hello World from thread =            2
 Hello World from thread =            5
 Hello World from thread =            3
 Hello World from thread =            4
 Hello World from thread =            0
 Hello World from thread =            1
 Hello World from thread =            6
 Hello World from thread =            7
 Number of threads =            8

Makefile

all: build run

build:
	gfortran omp_hello.f90 -fopenmp -lgomp
	f2py -c -m omp_hello omp_hello.f90 --f90flags="-fopenmp" -lgomp

run:
	@echo '********************'
	@echo 'running pure fortran'
	@echo '********************'
	./a.out
	@echo '********************'
	@echo 'running from python'
	@echo '********************'
	./run.py

clean:
	rm -rf a.out omp_hello.so.dSYM omp_hello.so

omp_hello.f90

program hello

  call hellofunc

end

subroutine HELLOfunc

  INTEGER :: NTHREADS, TID, OMP_GET_NUM_THREADS, OMP_GET_THREAD_NUM

  ! Fork a team of threads giving them their own copies of variables
  !$OMP PARALLEL PRIVATE(NTHREADS, TID)

  ! Obtain thread number
  TID = OMP_GET_THREAD_NUM()
  write(*,*) 'Hello World from thread = ', TID

  ! Only master thread does this
  IF (TID .EQ. 0) THEN
    NTHREADS = OMP_GET_NUM_THREADS()
    write(*,*) 'Number of threads = ', NTHREADS
  END IF

  ! All threads join master thread and disband
  !$OMP END PARALLEL
end 

run.py

#!/usr/bin/env python
import omp_hello

omp_hello.hellofunc()

Fyi,
It compiles with openMPi, using
f2py -c -m --fcompiler=gnu95 self_consistent_fortran self_consistent.f90 --f90flags="-march=native -fPIC -fopenmp -shared -ffixed-line-length-132 -O3 -g0 -lm" -lm --verbose

~kane

From: "Bennett, Kane" [email protected]
Date: Thursday, August 17, 2017 at 1:36 PM
To: "Wolfram Jr., Phillip" [email protected]
Subject: openMP on a cluster

Hi Phil,

Log shot, but I don’t suppose you recognize by any chance an error like this when compiling fortran with openMP on a cluster?

/usr/bin/ld: /home/kaneb/miniconda2/lib/libgomp.a(critical.o): relocation R_X86_64_32 against `.bss' can not be used when making a shared object; recompile with -fPIC
/home/kaneb/miniconda2/lib/libgomp.a: error adding symbols: Bad value
collect2: error: ld returned 1 exit status

Tried recompiling with fPIC, obviously, among various google searched answers, but to no avail. It’s on the new T-3 (dry side?) cluster that I’m trying to compile what works fine on my own machine.

~Kane